I have an external usb hard drive (WD Passport 1 TB) formatted (encrypted) for my Mac. Even before I encrypted it, I could only read but not write from my linux pc. After encryption not even that.
I need a new external HD for my linux pc, the one I am currently using is getting too old and is FAT32 formatted (from when I was still using Windows).
Questions:
If I want to encrypt an external usb HD which filesystem should I use?
Will I be able to use it on a multiboot linux (no windows) pc when encrypted? (Will I just be asked for password before use?)
Are there brands that are recommended or that I should avoid?

Yes, truecrypt to encrypt, but which filesystem that is read- and writeable by linux, mac osx and windows? NTFS, no because I hardly use windows. FAT32, no because limit of 4 GB filesize, ...
Someone told me to try UDF, the universal disk format, I wondered if anyone here has experience with it.

It's been a while since I used Truecrypt and I thought it included the filesystem, but it doesn't. Hardly is not te same as never, so I would still use NTFS for maximum portability, although exFAT is looking more interesting these days.

"Insanity: doing the same thing over and over again and expecting different results." (Albert Einstein)